Electric lamp bulb



Patented Dec. 24, 1935 PATENT OFFICE ELECTRIC LAMP BULB Gustav Herzberg, Newark, and William Ambrunn, Harrison, N. J assignors'to General Importing Company, East Newark, N. J a corporation of New Jersey No Drawing. Application August 2, 1933,

' Serial No. 683,290

5 description which is simple, economical and effective.

For a great many years past electric lamp bulbs have been frosted on the inside, usually by etching the inside surface of the bulb with hydro fluoric acid, compounds thereof or mixtures adiaipted by combination to produce hydrofluoric ac It is well known, of course, that hydrofluoric acid is well adapted to etch glass; nevertheless, this acid is such an active fluid and acts so rapidly and uniformly over the surface of the glass that it is difficult, if not impossible, to produce a frosting etch by' this means, probably for the reason that the action of hydrofluoric acid is so uniform and rapid that it leaves a surface almost as regular and smooth and transparent as the original surface.

It has, therefore, been proposed to use for an etching material instead of hydrofluoric acid as such, mixtures of various materials which produce in their reaction a small percentage of hydrofluoric acid and which possess in addition inert materials which more or less inhibit the too rapid action of the hydrofluoric acid and modify its effect. As a consequence of the irregular'action caused by the inhibiting materials, the result has been that instead of the even etch of a pure hydrofluoric acid solution which will not give a frosting etch by means of such mixtures, a frosting etch is produced but the inside surface of the bulb is etched in such a manner that it is full of sharp angular crevices which weaken the glass to such an extent that breakage occurs on very slight shocks. It has been proposed to a second time with a weaker solution of the same etching fluid. This is called a fortifying" treatment and is supposed to round out the angular crevices in the glass so that the bulb is much strengthened. Far from doing this, however, the

second so-called fortifying treatment merely accentuates and increases the number of angular crevices in the surface of the glass.

The present invention provides a process of frosting the inside surfaces of lamp bulbs and similar articles'in such a manner that the light transmitted from the lighting body through the bulb is greatly increased and that undue weakT ening of the glass of the bulb is avoided. As above stated, if hydrofluoric acid alone were used,

remedy this and to treat the interior of the bulb the bulb would not be unduly weakened but the action of this acid would be so uniform and regular that the etch would not be a frosting etch. The present invention may be carried out, indeed, by means of various etching fluids but no 6 second or fortifying treatment is necessary. The invention may be described as consisting of a treatment of the interior surface of the glass bulb with a 10% solution of hydrofluoric acid mixed with soda ash, an inhibiting material, and 10 water. This is followed by a treatment applying heat and moisture. The-secondtreatment may consist of spraying into the bulb water suitably heated, or steam.

' Fora lime glass the following has been found very successful:

frosting mixture 15 1 Per cent Hydrofiuoric acid, 10% solution 33 Ammonium bifluoride 25 Ammonium bicarbonate 12 20 Soda ash 15 Water 15 In this mixture the soda ash and the ammonium compounds, particularly the ammonium carbonate, have the effect of inhibiting of the hydrofluoric acid and of producing a finely grained surface. This frosting mixture is heated I to about 130 F. and is sprayed into the interior of the bulb intermittently for a period of approximately five seconds. In this time about three sprays of the mixture produce good results. When this treatment is finished, hot water may then be sprayed in also in about three sprays, intermittently applied, within a similar period of time. The temperature of the water should be, for good results, about 180 F. although a considerable range of temperature is permissible. The temperature should not be much less than 150 F. as in such case the glass will not be uniformly affected and may be very ununiform and very weak. After the treatment with hot water as described, cold water is sprayed into the interior a of the bulb continuously for about five seconds.

Instead of hot water, steam may be employed, with effects similar to that obtained by the use of hot water.

It will be evident, of course, that the second treatment does not act to any appreciable extent in diminution of the action of the etching mixture by diluting the mixture, but its value and effect is to be ascribed mainly to the effects of heat upon the residue of the etching mixture, making it more active.

,It will thus be seen that the process of this invention comprises a single treatment with an the action 5 erably higher.

etching mixture suitably heated, a following treatment with water suitably heated, or steam, and a final treatment with cold water. To realize the best results of the process, all three of these steps are necessary.

As it is the method of the present invention to frost the inside of the bulb without unduly weakening the glass, rather than to weaken the glass first and to "fortify it later, thetemperatures to be observed are of considerable importance. We have discovered that if the frosting process is carried out in the cold, a considerable crystallization is likely to take place in the mixture and the resulting frost is likely to be streaky and uneven and the bulb to be very weak. The same is -true, also, if the premises in which the process is conducted be very cold. Hydrofluoric acid, consequently, particularly when mixed with the inhibitors of the frosting mixture, is neither very active nor very uniformly active under cold conditions. In fact, we have found that the frosting mixture should be applied at a temperature of about F. or higher and that if the water applied in the second step of the process is much below F., the bulb will be weak and easily broken. In fact, we prefer toheat the water used in this treatment to about F. or even consid- Steam, for instance, may be employed with excellent results, which necessarily implies a much higher temperature.

There is, however, an upper limit beyond which the temperature of the water or steam in the second step should not be raised. This depends upon the strength of the frosting mixture and while no definite temperature can be stated from the nature of the case, it can be easily determined by the fact that at these undesirably high temperatures the action of the mixture produces effects approximating that of hydrofluoric acid alone. In other words, the result is not then a frosting etch but is an almost smooth, transparent etching of the inside of the bulb.

fl'he process, in fact, depends for its efficiency upon the effect of heat in activating the hydrofluoric acid in the frosting mixture and in the presence in this mixture of a quantity of inert or inhibiting material so correlated with the hydrofluoric acid and the temperatures employed that the etch is not only a frosting etch but a very,

finely and uniformly grained frosting etch on the interior. of the bulb and, furthermore, the finished interiorly frosted bulb is of a satisfactory commercial strength.

. The third or cold water treatment is not a mere cleansing of the interior of the bulb. This will be evident from the fact that when the second or hot water (or steam) treatment is completed, there is a' small but appreciable quantity of the more active elements of the frosting mixture, which under the temperature conditions existing will continue to act upon the glass before sufficient cooling has taken place to inhibit this action. The result is that the bulb is weakened from this continued action upon the glass to a point where it becomes unusable. Moreover, upon cool. ing, the various constituents of the frosting mixture, or, also, the constituents of the glass, such as silica and lime, or both the constituents of the mixture and the glass in combination, crystallize on the interior of the bulb and give it an unpleasant, unevenly crinkled appearance which renders it uncommercial for that reason alone.

If, however, the third step is quickly applied, that is the cold water treatment immediately following the hot water or steam treatment, the

- tacting the inner surface of the same during a continued action of the frosting mixture is arrested before it has weakened the glass unduly..

The formation of crystals or other deposits is also prevented.

It will be observed that the process comprises 5 four important features, viz: a frosting mixture of suitable strength and of suitable temperature, heat applied immediately thereafter in a suitable vehicle such as water or steam, a cooling and inhibiting treatment generally with cold water, 10 and a time element which for excellent results may be about flve seconds for each step.

It is well understoodin the art that an outside frosting of a lampv bulb results in a diminution of efliciency of about 20%. It is also well understood that in the case of a clear bulb incandescent lamp, when its efficiency falls off 20% it is more economical to destroy the lamp and obtain a new one. Indeed, when a clear bulb lamp has diminished, through use, in efliciency by 20% 20 from its initial efficiency, it is said to have reached the smashing point and should be destroyed. v

In the lamps of the present invention, however, there is so little light absorption by the 25 interior frosting of the bulb that the initial emciency is almost equivalent to that of a clear bulb lamp, the difference being only about 3% to 4%. The operating temperature of the lamp is thus much less than that of an outside frosted bulb 30 and this results in a longer life.

What we claim is:.

1. The process of applying a light-diflusing frosting to electric lamp bulbs consisting of intermittently contacting the inner surface of the same during an interval of the order of flve seconds with a heated frosting mix ure, and after such contact intermittently applying combined heat and moisture to said surface during a similar interval, and then treating the same continuously with cold water for approximately the same interval of time.

2. .The process of applying a light-diffusing frosting to electric lamp bulbs consisting of contacting the inner surface of the same during an interval of the order of five seconds with a heated frosting mixture, and then subjecting such surface to the action of heat and moisture only during a similar interval, and then treating the same withcold water for approximately the same interval of time. l

3. The process of applying a light-diffusing frosting to electric lamp bulbs consisting of conshort interval with a heated frosting mixture, and after such contact subjecting such surface to the action of heat and moisture only during a similar interval, and then treating the same with cold water for approximately the same interval of time.

4. The process of applying alight-diffusing frosting to thin-walled hollowglass bodies consisting of contacting against the inner surface oi the same a heated frosting mixture, and after such contact applying only heat and moisture to said surface, and then treating the same with cold water.

5. The process of applying a light-diffusing frosting to thin-walled hollow glass bodies consisting of contacting against the inner surface of the same a heated mixture containing hydrofluoric acid and acid salts, applying heat and moisture to said surface, and then treating the same with cold water.

6. The process of applying a light-diffusing frosting to thin-walled hollow glass bodies consisting of contacting against the'inner surface of the same a heated mixture hydrofluoric acid and acid salts; conveyin heat through an aqueous medium to the surface after such contact, and subsequently treating the same with cold water.

7. 11: pm of frosting thin-walled hollow glass bodies consisting of contacting the inner surface thereof witha frosting mixture, then applying a moist heat to said surface, and subsequently treating the same with cold water.

GUSTAV HERZBERG. WILLIAM AMBRUNN. 

